[PATCH] net: fs_enet: Implement NETIF_F_SG feature

From: Christophe Leroy
Date: Mon Feb 02 2015 - 12:07:20 EST


Freescale ethernet controllers have the capability to re-assemble fragmented
data into a single ethernet frame. This patch uses this capability and
implements NETIP_F_SG feature into the fs_enet ethernet driver.

On a MPC885, I get 53% performance improvement on a ftp transfer of a 15Mb file:
* Without the patch : 2,8 Mbps
* With the patch : 4,3 Mbps

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>

---
.../net/ethernet/freescale/fs_enet/fs_enet-main.c | 95 +++++++++++++++-------
drivers/net/ethernet/freescale/fs_enet/fs_enet.h | 1 +
2 files changed, 66 insertions(+), 30 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
index 9e2bcb8..a176287 100644
--- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
+++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
@@ -278,14 +278,20 @@ static int fs_enet_tx_napi(struct napi_struct *napi, int budget)
fep->stats.collisions++;

/* unmap */
- dma_unmap_single(fep->dev, CBDR_BUFADDR(bdp),
- skb->len, DMA_TO_DEVICE);
+ if (fep->mapped_as_page[dirtyidx])
+ dma_unmap_page(fep->dev, CBDR_BUFADDR(bdp),
+ CBDR_DATLEN(bdp), DMA_TO_DEVICE);
+ else
+ dma_unmap_single(fep->dev, CBDR_BUFADDR(bdp),
+ CBDR_DATLEN(bdp), DMA_TO_DEVICE);

/*
* Free the sk buffer associated with this last transmit.
*/
- dev_kfree_skb(skb);
- fep->tx_skbuff[dirtyidx] = NULL;
+ if (skb) {
+ dev_kfree_skb(skb);
+ fep->tx_skbuff[dirtyidx] = NULL;
+ }

/*
* Update pointer to next buffer descriptor to be transmitted.
@@ -299,7 +305,7 @@ static int fs_enet_tx_napi(struct napi_struct *napi, int budget)
* Since we have freed up a buffer, the ring is no longer
* full.
*/
- if (!fep->tx_free++)
+ if (++fep->tx_free >= MAX_SKB_FRAGS)
do_wake = 1;
has_tx_work = 1;
}
@@ -509,6 +515,9 @@ static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev)
cbd_t __iomem *bdp;
int curidx;
u16 sc;
+ int nr_frags = skb_shinfo(skb)->nr_frags;
+ skb_frag_t *frag;
+ int len;

#ifdef CONFIG_FS_ENET_MPC5121_FEC
if (((unsigned long)skb->data) & 0x3) {
@@ -530,7 +539,7 @@ static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev)
*/
bdp = fep->cur_tx;

- if (!fep->tx_free || (CBDR_SC(bdp) & BD_ENET_TX_READY)) {
+ if (fep->tx_free <= nr_frags || (CBDR_SC(bdp) & BD_ENET_TX_READY)) {
netif_stop_queue(dev);
spin_unlock(&fep->tx_lock);

@@ -543,35 +552,42 @@ static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev)
}

curidx = bdp - fep->tx_bd_base;
- /*
- * Clear all of the status flags.
- */
- CBDC_SC(bdp, BD_ENET_TX_STATS);
-
- /*
- * Save skb pointer.
- */
- fep->tx_skbuff[curidx] = skb;
-
- fep->stats.tx_bytes += skb->len;

+ len = skb->len;
+ fep->stats.tx_bytes += len;
+ if (nr_frags)
+ len -= skb->data_len;
+ fep->tx_free -= nr_frags + 1;
/*
* Push the data cache so the CPM does not get stale memory data.
*/
CBDW_BUFADDR(bdp, dma_map_single(fep->dev,
- skb->data, skb->len, DMA_TO_DEVICE));
- CBDW_DATLEN(bdp, skb->len);
+ skb->data, len, DMA_TO_DEVICE));
+ CBDW_DATLEN(bdp, len);
+
+ fep->mapped_as_page[curidx] = 0;
+ frag = skb_shinfo(skb)->frags;
+ while (nr_frags) {
+ CBDC_SC(bdp,
+ BD_ENET_TX_STATS | BD_ENET_TX_LAST | BD_ENET_TX_TC);
+ CBDS_SC(bdp, BD_ENET_TX_READY);
+
+ if ((CBDR_SC(bdp) & BD_ENET_TX_WRAP) == 0)
+ bdp++, curidx++;
+ else
+ bdp = fep->tx_bd_base, curidx = 0;

- /*
- * If this was the last BD in the ring, start at the beginning again.
- */
- if ((CBDR_SC(bdp) & BD_ENET_TX_WRAP) == 0)
- fep->cur_tx++;
- else
- fep->cur_tx = fep->tx_bd_base;
+ len = skb_frag_size(frag);
+ CBDW_BUFADDR(bdp, skb_frag_dma_map(fep->dev, frag, 0, len,
+ DMA_TO_DEVICE));
+ CBDW_DATLEN(bdp, len);

- if (!--fep->tx_free)
- netif_stop_queue(dev);
+ fep->tx_skbuff[curidx] = NULL;
+ fep->mapped_as_page[curidx] = 1;
+
+ frag++;
+ nr_frags--;
+ }

/* Trigger transmission start */
sc = BD_ENET_TX_READY | BD_ENET_TX_INTR |
@@ -582,8 +598,22 @@ static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev)
* yay for hw reuse :) */
if (skb->len <= 60)
sc |= BD_ENET_TX_PAD;
+ CBDC_SC(bdp, BD_ENET_TX_STATS);
CBDS_SC(bdp, sc);

+ /* Save skb pointer. */
+ fep->tx_skbuff[curidx] = skb;
+
+ /* If this was the last BD in the ring, start at the beginning again. */
+ if ((CBDR_SC(bdp) & BD_ENET_TX_WRAP) == 0)
+ bdp++;
+ else
+ bdp = fep->tx_bd_base;
+ fep->cur_tx = bdp;
+
+ if (fep->tx_free < MAX_SKB_FRAGS)
+ netif_stop_queue(dev);
+
skb_tx_timestamp(skb);

(*fep->ops->tx_kickstart)(dev);
@@ -917,7 +947,7 @@ static int fs_enet_probe(struct platform_device *ofdev)
}

fpi->rx_ring = 32;
- fpi->tx_ring = 32;
+ fpi->tx_ring = 64;
fpi->rx_copybreak = 240;
fpi->napi_weight = 17;
fpi->phy_node = of_parse_phandle(ofdev->dev.of_node, "phy-handle", 0);
@@ -955,7 +985,8 @@ static int fs_enet_probe(struct platform_device *ofdev)

privsize = sizeof(*fep) +
sizeof(struct sk_buff **) *
- (fpi->rx_ring + fpi->tx_ring);
+ (fpi->rx_ring + fpi->tx_ring) +
+ sizeof(char) * fpi->tx_ring;

ndev = alloc_etherdev(privsize);
if (!ndev) {
@@ -978,6 +1009,8 @@ static int fs_enet_probe(struct platform_device *ofdev)

fep->rx_skbuff = (struct sk_buff **)&fep[1];
fep->tx_skbuff = fep->rx_skbuff + fpi->rx_ring;
+ fep->mapped_as_page = (char *)(fep->rx_skbuff + fpi->rx_ring +
+ fpi->tx_ring);

spin_lock_init(&fep->lock);
spin_lock_init(&fep->tx_lock);
@@ -1007,6 +1040,8 @@ static int fs_enet_probe(struct platform_device *ofdev)

netif_carrier_off(ndev);

+ ndev->features |= NETIF_F_SG;
+
ret = register_netdev(ndev);
if (ret)
goto out_free_bd;
diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet.h b/drivers/net/ethernet/freescale/fs_enet/fs_enet.h
index 3a4b49e..f184d8f 100644
--- a/drivers/net/ethernet/freescale/fs_enet/fs_enet.h
+++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet.h
@@ -134,6 +134,7 @@ struct fs_enet_private {
void __iomem *ring_base;
struct sk_buff **rx_skbuff;
struct sk_buff **tx_skbuff;
+ char *mapped_as_page;
cbd_t __iomem *rx_bd_base; /* Address of Rx and Tx buffers. */
cbd_t __iomem *tx_bd_base;
cbd_t __iomem *dirty_tx; /* ring entries to be free()ed. */
--
2.1.0

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